O2 sensor change, mpg improvement?

[nigelb]

reading some of the posts i noticed that a few people were saying by changing the O2 sensor on the front manifold they were getting better gas mileage, with a lifespan of around 50k before the sensor degraded.
my STS has 188k miles on it and out of curiosity i ordered a new delco sensor from rock auto.
i don't know whether i have big hands but i seem to have a hell of a time undoing the connectors on these N*'s.
anyway i've fitted the sensor now i'll see what happens.
my average consumption is 15 mpg so even an increase of 1mpg will be a boon.
my average journey time is 15 minutes so i don't really do much high speed cruising.
been running around a little this afternoon and the average has gone up to 15.2. (that included a 100mph spurt against an 850 beemer, lord knows where we found the space to do that!) i guess it may take a while for the pcm to reset itself so i expect to see very little increase for a few days.
i have a 190 mile trip tomorrow and i know i'll get a bit of a false average from it as it's not my usual pattern of driving, although it usually only takes a day or 2 to drop back down to around 15mpg.
i must be mad, gas is EXPENSIVE here, its currently around $1.62 for a LITER, whats that, about $6.15 a US gallon and i drive a 15mpg cadillac, point me to that padded cell

hey, now you know why i paid $70 for a sensor that wasn't pulling codes, i need all the help i can get.

by the way, my consumption of 15mpg is for a US gallon, they sold the STS here and NEVER updated the fuel computer to display in Imperial gallons, we get 4.54 liters to a gallon, all my figures need multiplying by 1.2 to change from US to Imperial (verified by comparing readings with the metric setting), so in reality i get 18 miles per imperial gallon which compares OK to a big merc or bmw etc.

[ejguillot]

When you say that you bought "A sensor", did you buy 1 o2 sensor, or 2 (1 for each bank of cylinders)? I put 2 sensors in my STS last month (and 8 spark plugs), i'm averaging between 19-20 miles a US gallon.

[Ranger]

Originally Posted by ejguillot

When you say that you bought "A sensor", did you buy 1 o2 sensor, or 2 (1 for each bank of cylinders)? I put 2 sensors in my STS last month (and 8 spark plugs), i'm averaging between 19-20 miles a US gallon.

What about the other two?

[nigelb]

i was being tight with my cash and only changed 1 sensor. i did contemplate doing both but the general feeling from posters was that only 1 sensor really changed the fuelling, the other was there as a check.
now i really don't know if what was posted was true, but it seemed very logical to me.

if by changing just one sensor i get an improvement i'll be happy. if the mileage doesn't get better then i'll change the other sensor and see what happens.

[nigelb]

Ranger, i must be lucky, the FSM only shows 3 O2 sensors for my '00.
one in each manifold and the other is after the cat.

anyway, been out yesterday and today doing some of my 'normal' drive patterns.
the average has settled for the moment on 16.9mpg.
i guess i need a few more days to see if it drops.

[krimson_cardnal]

Who's your local? K_C

[Ranger]

Originally Posted by nigelb

Ranger, i must be lucky, the FSM only shows 3 O2 sensors for my '00.
one in each manifold and the other is after the cat.

anyway, been out yesterday and today doing some of my 'normal' drive patterns.
the average has settled for the moment on 16.9mpg.
i guess i need a few more days to see if it drops.

Interesting. Guess they made another change without telling me. I gotta find an '03 FSM.

[clarkz71]

Originally Posted by Ranger

What about the other two?

The "post" converter o2 sensor won't affect mpg. It only verifys catalytic converter efficiency.